二氧化碳提纯液化新工艺技术研究

Study on New Technology of Carbon Dioxide Purification and Liquefaction

利用二氧化碳气源组分之间相对挥发度的差异,采用低温精馏和分级制冷工艺,实现二氧化碳与其他杂质的分离及液化;同时脱除氮气、氢气、甲烷、水、重烃等组分。对丙烷、氨及氟利昂制冷剂的制冷性能进行系统对比和分析,与常规分子筛脱水后直接制冷液化工艺相比,该工艺具有装置占地面积小、单位产品能耗低、液体二氧化碳产品纯度高等优点。采用ASPEN HYSYS工艺模拟软件,以某天然气净化厂MDEA脱碳装置再生尾气为研究对象,对比了不同工况下,低温精馏装置能耗、产品纯度的变化。计算在不添加防冻剂的条件下,保证脱重塔不发生冻堵的临界操作压力。该研究对合成氨装置和天然气脱碳装置的二氧化碳尾气回收、提纯及液化具有借鉴意义。

The separation and liquefaction of carbon dioxide from other impurities are realized by low temperature distillation and fractional refrigeration process based on the difference of relative volatilization among carbon dioxide gas source components.Nitrogen,hydrogen,methane,water,heavy hydrocarbon,and other components can be removed at the same time.The refrigeration performance of propane,ammonia,and freon refrigerant are compared and analyzed systematically.Compared with the conventional cooling liquefaction process after zeolite dehydration,this process has the advantages of needing small area,low energy consumption per unit product,and high purity of liquid carbon dioxide products.ASPEN HYSYS process simulation software is used to study the regenerated tail gas of MDEA decarbonization unit in a natural gas purification plant.The changes of energy consumption and product purity of low-temperature distillation unit are compared under different working conditions.To ensure that the deweighting tower does not freeze up and block,the critical operating pressure without adding antifreeze is calculated.This study has a reference significance for carbon dioxide tail gas recovery,purification and liquefaction in ammonia plants and natural gas decarbonization plants.